Flow cytometry is an important analytical tool for detecting characteristic fluorescence emission intensities from cellular components such as DNA, RNA, proteins, enzymes, and lipids. The components are stained with fluorescent dyes, antigenic determinants labeled with antibodies conjugated to fluorochrome, hybridized to DNA sequences labeled with fluorescent probes, or labeled with some other type of fluorescent labeling technique. The resulting emission intensity is measured at high speed on a cell-by-cell basis. Fluorescence signal intensity, signal width and area are among the fluorescence emission characteristics measured by the cytometer. The device works by measuring the desired characteristic at specified wavelength regions within the fluorescence spectra when the stained cells or particles intersect a cw laser or arc lamp excitation source. Conventional flow cytometry has become an important clinical diagnostic and biomedical research tool, demanding ever-expanding capabilities to meet clinical and research needs.
To be studied, the labeled biological material is added to a liquid which is termed "sheath fluid." The sheath fluid and biological material mixture is passed through the fluidic passages of the flow cytometer, where the desired measurements are made. The apparatus for handling the sheath fluid includes a reservoir for unused or clean sheath fluid and a reservoir for waste sheath fluid which has passed through the fluidic passages of the flow cytometer. Fluid is pumped from the clean fluid reservoir through the fluidic passages to the waste fluid reservoir. The problem with existing sheath fluid reservoirs is the space they occupy; essentially twice the volume of the sheath fluid being used.
Accordingly, it is the object of the present invention to reduce the combined volumes of the two sheath fluid containers by, essentially, 50%.
It is another object of the invention to consolidate the two sheath fluid containers into a single container, preferably a disposable container.
It is a further object of the invention to minimize the combined volumes of the two sheath fluid containers by the use of collapsible and expandable reservoirs in the same container; wherein as the clean fluid reservoir collapses, the waste reservoir expands. Thus, the same physical space (or volume) is used to store both clean and waste sheath fluid, thereby halving the volume utilized by prior art sheath fluid containers.
It is a further object of the invention to simplify the packaging and handling of sheath fluid, with two reservoirs packaged in a single disposable container (e.g., a cardboard box).
Flexible containers for liquids which collapse as liquid is removed from the container are known. However, no applications of flexible containers for flow cytometry are known. Furthermore, there are numerous patents drawn to the flow cytometry art, such as U.S. Pat. No. 5,270,540 which discloses a "phase-sensitive" flow cytometer, allowing the use of multiple fluorochromes during one measuring cycle. No patents in this area were found which suggest any alterations to the standard sheath fluid reservoir system.